The present article deals with possible global and regional changes of climate in the 21st century with different scenarios of natural and anthropogenic impacts given in comparison to the estimates of contemporary changes according to observations data. The results of analysis of numerical simulations with global climatic models and of the more detailed regional simulations are described. Possible changes are analyzed, taking into account the carbon cycle in climatic models, including the methane cycle. Together with temperature the changes of precipitation, river runoff, bioproductivity of terrestrial ecosystems are estimated. Moreover, the article describes the characteristics of extreme regimes, including extreme precipitation, droughts and fires. The relative contribution of natural (solar and volcanic activity) and anthropogenic factors, for the entire globe and for the regions with considerable temperature changes over the last decades are also evaluated.